Commit 5bcaf3e1 authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini
Browse files

KVM: x86/mmu: Account NX huge page disallowed iff huge page was requested 



Condition the accounting of a disallowed huge NX page on the original
requested level of the page being greater than the current iterator
level.  This does two things: accounts the page if and only if a huge
page was actually disallowed, and accounts the shadow page if and only
if it was the level at which the huge page was disallowed.  For the
latter case, the previous logic would account all shadow pages used to
create the translation for the forced small page, e.g. even PML4, which
can't be a huge page on current hardware, would be accounted as having
been a disallowed huge page when using 5-level EPT.

The overzealous accounting is purely a performance issue, i.e. the
recovery thread will spuriously zap shadow pages, but otherwise the bad
behavior is harmless.

Cc: Junaid Shahid <junaids@google.com>
Fixes: b8e8c830 ("kvm: mmu: ITLB_MULTIHIT mitigation")
Signed-off-by: default avatarSean Christopherson <sean.j.christopherson@intel.com>
Message-Id: <20200923183735.584-6-sean.j.christopherson@intel.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 3cf06612

arch/x86/kvm/mmu/mmu.c

+2 −1
Original line number Diff line number Diff line
@@ -3383,7 +3383,8 @@ static int __direct_map(struct kvm_vcpu *vcpu, gpa_t gpa, u32 error_code, 
					      it.level - 1, true, ACC_ALL);



			link_shadow_page(vcpu, it.sptep, sp);

			if (is_tdp && huge_page_disallowed)

			if (is_tdp && huge_page_disallowed &&

			    req_level >= it.level)

				account_huge_nx_page(vcpu->kvm, sp);

		}

	}

arch/x86/kvm/mmu/paging_tmpl.h

+1 −1
Original line number Diff line number Diff line
@@ -708,7 +708,7 @@ static int FNAME(fetch)(struct kvm_vcpu *vcpu, gpa_t addr, 
			sp = kvm_mmu_get_page(vcpu, base_gfn, addr,

					      it.level - 1, true, direct_access);

			link_shadow_page(vcpu, it.sptep, sp);

			if (huge_page_disallowed)

			if (huge_page_disallowed && req_level >= it.level)

				account_huge_nx_page(vcpu->kvm, sp);

		}

	}